A Comprehensive Analysis of Calmodulin-Like Proteins of Glycine max Indicates Their Role in Calcium Signaling and Plant Defense Against Insect Attack

Abstract

The calcium (Ca²⁺) signaling is a crucial event during plant-herbivore interaction, which involves a transient change in cytosolic Ca²⁺ concentration, which is sensed by Ca²⁺-sensors, and the received message is transduced to downstream target proteins leading to appropriate defense response. Calmodulin-like proteins (<i>CMLs</i>) are calcium-sensing plant-specific proteins. Although <i>CMLs</i> have been identified in a few plants, they remained uncharacterized in leguminous crop plants. Therefore, a wide-range analysis of <i>CMLs</i> of soybean was performed, which identified 41 true CMLs with greater than 50% similarity with <i>Arabidopsis CMLs</i>. The phylogenetic study revealed their evolutionary relatedness with known <i>CMLs</i>. Further, the identification of conserved motifs, gene structure analysis, and identification of <i>cis</i>-acting elements strongly supported their identity as members of this family and their involvement in stress responses. Only a few <i>Glycine max CMLs (GmCMLs)</i> exhibited differential expression in different tissue types, and rest of them had minimal expression. Additionally, differential expression patterns of <i>GmCMLs</i> were observed during <i>Spodoptera litura</i>-feeding, wounding, and signaling compound treatments, indicating their role in plant defense. The three-dimensional structure prediction, identification of interactive domains, and docking with Ca²⁺ ions of <i>S. litura</i>-inducible GmCMLs, indicated their identity as calcium sensors. This study on the characterization of <i>GmCMLs</i> provided insights into their roles in calcium signaling and plant defense during herbivory.